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Soho bindings

What is a binding?

Soho lets you inject any binding into the template when it is evaluated to produce HTML. A classic example is to have a variable navigation that highlights the current page:

<ul id="navigation">
  <li>
    <a href="/about.html">About</a>
  </li>
  <li class="current">
    <a href="/install.html">Install</a>
  </li>
</ul>

In TAL, you would want to generate it with this:

<ul id="navigation">
  <li tal:repeat="item context/getNavigation"
      tal:attributes="class item/css_class | nothing">
    <a tal:attributes="href item/href;"
       tal:content="item/title"/>
  </li>
</ul>

The only issue here is to inject getNavigation in the template. With Soho, you only have to write a Python module and define the bindings that you want. In this example, we could have a hard-coded, context-dependent navigation with the following bindings module:

import re

NAVIGATION = [{'title': 'About',
               'href': '/about.html,
               'selected': re.compile('/about\.html')},
              {'title': 'Install',
               'href': '/install.html,
               'selected': re.compile('/install\.html')},
              ]


def getNavigation(context):
    """A hard-coded navigation menu."""
    navigation = [m.copy() for m in NAVIGATION]
    for item in navigation:
        selected = item.get('selected')
        if selected and selected.match(context.path):
            item['css_class'] = ' current'
    return navigation

bindings = (getNavigation, )

As you can see, this is a normal Python module, so you can use other Python packages (e.g. the re package), as usual.

Save this code in a mybindings.py file somewhere and add this line to Soho configuration file:

bindings = /path/to/mybindings.py

Note that these functions will be bound to the Context class, so the first parameter of these functions should be the context.

Available bindings

Soho currently comes with a set of bindings.

>>> from soho.bindings import *

Pygments-related bindings

Pygments is a Python module that can highlight code in several languages. Soho comes with a handful of Pygments-related functions which can be used as bindings.

The getPygmentsLexers function tries to find Pygments "sourcecode" directive in your content and return the lexers that are used.

>>> source = '''\
... This is a piece of Python code:
...
... .. sourcecode:: python
...
...     def foo(bar=None):
...         print bar
...
... And a piece of reStructuredText:
...
... .. sourcecode:: rest
...
...     **this text in bold**
...
... '''
>>> class FakeContext:
...     def __init__(self, source):
...         self.source
>>> getPygmentsLexers(FakeContext(source))
('python', 'rest')

There is also a getAvailablePygmentsLexers function which lists all Pygments lexers that are available. These bindings can be quite convenient to conditionally include Pygments CSS files. For example, in the page template, you would use them like this:

<tal:pygmentscss tal:define="used_lexers context/getPygmentsLexers"
                 tal:repeat="lexer context/getAvailablePygmentsLexers">
  <link tal:condition="python: lexer in used_lexers"
        tal:attributes="href string:/css/pygments-${lexer}.css"
        rel="stylesheet" type="text/css">
</tal:pygmentscss>